Ultrasonic propagation medium



A ril 14, 1970 R. A. TRACY 3,506,934

ULTRASONI G PROPAGATION MEDIUM Filed May 24, 1967 INVENTOR.

ROBERT A-TRACY BY M W AGENT United States Patent 3,506,934 ULTRASONIC PROPAGATION MEDIUM Robert A. Tracy, Castro Valley, Califl, assignor to The Singer Company, a corporation of New Jersey Filed May 24, 1967, Ser. No. 640,998

Int. Cl. H03h 7/30; C22c 9/00 U.S. Cl. 333--30 2 Claims ABSTRACT OF THE DISCLOSURE An ultrasonic delay line comprised of a pulse propagating medium having the characteristics of low hysteresis loss, high thermal coefficient of time delay, relatively slow propagation speed, and low temperature annealability. The pulse propagating medium isQconstructed of a copper base allow consisting essentially of about 97% copper and about 2% beryllium.

BackgroundField of invention This invention pertains to an improved ultrasonic delay line, and more particularly concerns a delay line having a high thermal coeflicient of time delay and improved transmission characteristics in addition to easy manufacturability.

Background-Prior art In the past, ultrasonic delay lines for use in electronic data processors, radar, and the like, included an ultrasonic pulse propagating medium comprised of material that generally is insensitive to temperature variations, i.e., it has a low thermal coefi'icient of time delay. A typical pulse propagating medium is well-known NiSpan C which has a thermal coefiicient of time delay of from about fifteen p.p.m./ C. (parts per million per degree centigrade) to about five p.p.m./ C. However, recent advances in the use of ultrasonic delay lines have generally rendered it unnecessary that the pulse propagating medium have a relatively low thermal coefiicient of time delay characteristic.

In addition, recent advances in electronic systems utilizing ultrasonic delay lines have rendered it desirable and advantageous that the thermal coefiicient of time delay characteristic of the pulse propagating medium be relatively high. For example, in some electronic systems hav ing an ultrasonic delay line, the pulse propagating medium is heated directly, as by passing electric current through it, or indirectly, as by wrapping a resistance element about the medium, to rapidly and efiiciently change the effective delay time of the medium so as to be in synchronism with a source of recurring electrical signals.

Summary Briefly stated, the present invention is accomplished by forming the pulse propagating medium of an ultrasonic delay line from a material that has a relatively high thermal coefficient of time delay characteristic, a low pulse attenuation characteristic, a'low initial cost, and is easily and economically manufactured, such as, for example, beryllium copper alloy.

It is, therefore, an object of the present invention to provide an improved ultrasonic delay line.

Another object of the present invention is to provide an improved ultrasonic pulse propagating medium.

The features of novelty that are considered characteristic of this invention are set forth with particularity in the appended claims. The organization and method of operation of the invention may best be understood from the following description when read in connection with the accompanying drawing.

3,506,934 Patented Apr. 14, 1970 ice Brief description of the figure The figure illustrates an ultrasonic delay line of the present invention.

Description of a preferred embodiment In the figure an ultrasonic delay line 10 is shown as including a spirally wound pulse propagating wire, or medium, 12, the turns of which are held in a generally flat plane by means of a plurality of mounting members 14 secured to a generally rigid base member, or frame, 16; mounting members 14 may be of the type shown and described in copending application S.N. 533,750 filed Feb. 2, 1966 (a continuation of U.S. application S.N. 319,197, filed Aug. 28, 1963 and now abandoned) now U.S. Patent No. 3,327,252 by George H. Hare and assigned to the same assignee as the present application.

One end of the wire 12 is operatively coupled to an input transducer 18 which includes a pair of magnetostrictive ribbons 20 and a reflection absorption means 22.

The other end of the wire 12 is operatively coupled to an output transducer 24 which includes a pair of magnetostrictive ribbons 26 and a reflective absorptive means 28.

Full details of the construction and operation of the particular input transducer 18 and output transducer 24 are not necessary to the present invention, and are not set forth herein. If desired, reference may be made to U.S. Patent No. 3,241,090, A. L, Bastian, for a brief description of the operation and construction of an ultrasonic delay line having input and output transducers of the type shown in the figure of this application. Other types of input and output transducers may be utilized as desired by those skilled in the art to which the present disclosure pertains.

An electrical signal applied to the input transducer 1 8 by means of electrical leads (not shown) from a source of electrical data indicative signals will initiate a mechanical disturbance on the wire 12 at the point of contact between the ribbons 20 and the wire. Such disturbance, generally termed a pulse, will propagate itself along the spiraled wire toward the output transducer 24. When the pulse arrives at the point of connection of the output transducers ribbons 26 and the wire 12, an electrical signal is generated and transmitted over electrical leads (not shown) to any desired utilization device (not shown).

The transit, or propagation time, commonly termed delay time, of a pulse on the wire 12 is, in general, dependent upon the particular material comprising the wire, the manufacturing treatment according the material, and the heat content or temperature of the wire. Such propagation time is generally a constant value at a given temperature. However, an increase or decrease in temperature of the wire from a given value will have the eflect of either increasing or decreasing the propagation time. A change in propagation time with a change in one unit of temperature of the pulse propagating medium is referred to as thermal coefficient of time delay, and is generally expressed as parts per million per degree centigrade. Thus, if a wire 12 comprised of a particular material and having a certain length L at a certain temperature T, increases in temperature by one degree centigrade, the delay or propagation time DT of a pulse through the entire length of wire will increase a certain amount.

In certain ultrasonic delay line applications it is desirable and highly advantageous that the pulse propagating medium have a relatively large thermal coefiicient of time delay as compared with the thermal coefficient of time delay of about 10i5 p.p.m./ C. for the commonly used pulse propagating medium material, NiSpan C. For example, in copending application S. N. 635,202, filed on May 1, 1967, by Robert A. Ragen entitled Delay Line Transit Time Control System, now U.S. Patent No. 3,435,351, issued March 3, 1969 and assigned to the same assignee as the present application, there is disclosed and claimed a system for regulating the delay or propagation time of an ultrasonic delay line, wherein controlled amounts of heat are periodically applied'to the pulse propagating medium for increasing its total pulse propagating time. In such a system it is desirable and advantageous that the thermal coefficient of time delay of the pulse propagating medium be high so that only relatively small amounts of heat need be applied to the medium for rapid control response. In such a system a relatively large thermal coefiicient of time delay provides very rapid response to control heat and a consumption of small amounts of power.

It has been discovered that a pulse propagating medium 12 comprised of beryllium copper alloy, preferably annealed or heat-treated as described below, provides a relatively high thermal coefficient of time delay as compared with the usual thermal coefiicient of time delay encountered in NiSpan C material as set forth above.

For example, in one embodiment, a beryllium copper alloy pulse propagating medium, or wire, 12 was comprise-d of 1.9% beryllium by weight, 97% copper by weight, a minimum of 0.2% by weight of either nickel or cobalt, and the remainder weight comprised of unidentified impurities. Other pulSe propagating wires 12 were made wherein the beryllium component ranged from about 1.8% to about 2.02% by weight. Still other embodiments have included a maximum 0.6% by weight of a mixture of nickel, cobalt and iron. Such beryllium copper alloy pulse propagating wire or medium, comprised 'as set forth above, has a thermal coefficient of time delay of about 176 parts per million per degree centigrade.

The alloy set forth above and hereinafter simply referred to as beryllium copper alloy, has been found to have a pulse propagation speed at a room temperature of 27 C. of about 0.093 inch per microsecond sec.); such speed of pulse propagationis relatively slow as compared with the pulse propagation speed in NiSpan C which is about 0.114 inch per microsecond at 27 C. The relatively slow propagation time of beryllium copper alloy is highly advantageous in that a much shorter length of wire 12 may be utilized to provide the same amount of delay as with a NiSpan C wire. The shorter length beryllium copper alloy wire provides for packaging the delay line in a smaller space.

Further, it has been noted that beryllium copper alloy has the characteristic of very low elastic hysteresis loss, i.e., a mechanical disturbance is propagated through the material with a relatively small amount of damping or attenuation. This characteristic is very desirable in an ultrasonic delay line.

The characteristics of relatively low pulse propagation speed, and low hysteresis loss in beryllium copper alloy offers the advantage of relatively close or dense pulse packing in the delay line. In other words, successive pulses may be separated, temporally and physically, by a smaller amount than has heretofore been possible with the usual delay material such as NiSpan C. In one embodiment the bit or pulse packing density was about two and a half times that attainable with NiSpan C.

In addition to the foregoing advantages of beryllium copper alloy, it has been found that substantially less time and greater ease in manufacturing is accomplished. in the usual manufacture of a spiraled or coiled delay line wire 12, like that shown in the figure, the coiled wire is heated in a furnace for annealing purposes. The beryllium copper alloy medium used in one embodiment of this invention was annealed at about 600 F. for about two hours in an ordinary atmosphere (air) for maximum aardness. This is contrasted with annealing of a coiled ielay line wire comprised of NiSpan C, which is usually performed at 1350" F. for aboutthirty minutes in anatmosphere consisting of a mixture of hydrogen and nitrogen gases.

In addition, a beryllium copper alloy delay line wire 12 has been found to not require a high gloss or bright surface for efficient transmission of pulses. This is contrasted with NiSpan C material which requires a bright smooth surface finish to maximize efiicient pulse propagation.

While the principles of the invention have been made clear in the illustrative embodiments, there will be obvious to those skilled in the art many modifications in structure, arrangement, proportions, the elements, materials and components, used in the practice of the invention, and otherwise, which are adapted for specific environments and operating requirements, without departing from these principles. The appended claims are, therefore, intended to cover and embrace any such modifications within the limits only of the true spirit and scope of the invention.

What is claimed is:

1. In combination in a delay line apparatus:

a pulse propagation medium having a first end portion and a second end portion;

first transducer means for launching pulses on said medium at one of said end portions;

second transducer means for receiving pulses at the other one of said end portions;

said medium consisting essentially of an alloy of about 97% by weight of copper, about 2% by weight of beryllium and a minimum of 0.2% by weight of a material selected from the group consisting of nickel and cobalt.

wherein pulses propagated on said medium travel at a speed of about .093 inch per microsecond when said medium is at a temperature of substantially 27 C. and wherein a change of temperature of said medium changes the speed of propagation of said pulses on said medium by about 176 parts per million per degree centigrade change in temperature. 2. In combination in a delay line apparatus: a pulse propagation medium having a first end portion and a second end portion; first transducer means for launching pulses on said medium at one of said end portions;

second transducer means for receiving pulses at the other one of said end portions;

said medium consisting essentially of an alloy of about 97% by weight of copper, about 2% my weight of beryllium, and a maximum of 0.6% by weight of a mixture of nickel, cobalt, and iron; wherein pulses propagated on said medium travel at a speed of about .093 inch per microsecond when said medium is at a temperature of substantially 27 C. and wherein a change of temperature of said medium changes the speed of propagation of said pulses on said medium by about 176 parts per million per degree centigrade change. in temperature.

References Cited UNITED STATES PATENTS 2,162,308 6/1939 Jenny -153 3,327,252 6/1967 Hare 333 30 3,400,340 9/1968 Pap-adakis 148-39 OTHER REFERENCES Materials & Methods, April 1950, pp. 76-80.

CHARLES N. LOVELL, Primary Examiner U.S. Cl. X.R. 

